Conventional cabinets housing a central processing unit of a computer are usually large, heavy and inconvenient to shift from one place to another. To facilitate movement, wheels may be mounted on the bottom of the cabinet. Usually, a braking structure is provided for at least two of the wheels to ensure that the cabinet remains fixed in place when operational. This braking structure generally comprises an engaging lever and locking element. When the engaging lever is pressed, it actuates the locking element to engage with the wheel thereby impeding rotation of the wheel, and thus braking the cabinet. Conversely, lifting the engaging lever disengages the locking element to permit the wheel to rotate freely so that the cabinet can be moved. Generally, a traditional engaging structure is provided for each wheel independently, requiring successive operations for each wheel to enable and disable movement of the cabinet. It is inconvenient to operate such a structure, and also, it may be difficult to distinguish if the wheels of the cabinet are locked or unlocked.